1. Field of the Invention
The present invention relates to an actuation system and a helicopter.
2. Description of Related Art
A helicopter has a rotary wing on an airframe thereof and is possible to perform vertical ascent and decent, forward and backward movement, and hovering. The helicopter is desired to have an improved operability. FIG. 1 shows a rotary wing of a convention helicopter. The rotary wing 100 includes a rotor 101, blades 102-1 and 102-2, bearings 103-1 and 103-2, a swash plate 104, and a pitch change 105. The rotor 101 is arranged in an upper portion of the airframe of the helicopter (not shown) and rotates around a rotation axis 106 with respect to the airframe. The blades 102-i (i=1, 2) form a wing. The bearings 103-i are supported by the rotor 101 and support blades 102-i rotatably around rotation axes 107-i. The swash plate 104 is supported by the rotor 101 to be movable in up and down directions along the rotation axis 106. The pitch change 105 is connected to a part of the blade 102-i and a part of the swash plate 104 and maintains a distance between the part of the blades 102-i and the part of the swash plate 104 to be a constant.
The blades 102-i generate a lift force when the rotor 101 rotates. That is to say, the rotary wing 100 generates propulsion of the helicopter through rotation of the rotor 101. In this case, the swash plate 104 can be moved in the direction 108 to change the lift force of the blades 102-i, thereby improving the operability of the helicopter. For the helicopter, it is desired to reduce vibrations and noises more.
It is known that the helicopter can reduce vibrations and noises more by driving a flap to deform an airfoil of the blades. FIG. 2 shows a driving unit 110 for driving a flap. The driving unit 110 includes a hydraulic source 111, a hydraulic pipe 112, and a hydraulic cylinder 113. The hydraulic source 111 is arranged on the airframe of the helicopter and pressurizes hydraulic fluid to generate a predetermined hydraulic pressure. The hydraulic pipe 112 transmits the hydraulic pressure from the hydraulic source 111 to the hydraulic cylinder 113 by passing the hydraulic fluid. The hydraulic cylinder 113 drives the flap 114 with the hydraulic pressure of the hydraulic fluid. In this case, in order to transmit the hydraulic pressure from the airframe to the rotating blade, a complex mechanism is required. The driving unit 110 is desired to have more simple structure and to be arranged inside the blade.
FIG. 3 shows a driving unit 120 arranged inside the blade. The driving unit 120 is composed of a so-called bimorph type piezoactuator 121 made by laminating piezoelectric elements which are deformed based on applied voltage. The driving unit 120 is deformed into a form depending on a voltage applied to each of the piezoelectric elements so that a flap 122 is driven to a position. The driving unit 120 is desired to have a larger stroke (movable range).
One conventionally known driving unit uses a laminate type piezoactuator to enlarge the movable range by applying leverage. Such a driving unit has a small driving force compared with a bimorph type piezoactuator for which the leverage is not applied and may have a large error because of a mechanical fluctuation of the leverage. The driving unit is desired to have a strong output force and have higher precision.
Japanese Laid Open Patent Application (JP-P2004-66990A) discloses a flap driving unit suitable for a unit for driving flaps provided for rotor blades. In the flap driving unit in the rotor blades, each of first and second actuator units is arranged on the rotor blade along a direction of the length of the rotor blade and has an actuator for generating a driving force the stretching and shortening. A first rotation section is provided between the first actuator unit and the second actuator unit and rotates the flaps into one direction in response to the driving force of the first actuator unit. A second rotation section is provided between the first actuator unit and the second actuator unit and rotates the flaps in another direction in response to the driving force of the second actuator unit.
Japanese Laid Open Patent Application (JP-P2003-530267A) discloses a piezoelectric control apparatus for controlling flaps of a rotor blade of a helicopter, which has functionality in high level and certainty of the operation. The piezoelectric control apparatus has a piezoelectric element device including at least a laminated piezoelectric actuator and a force transmission frame connected to the piezoelectric element device. The force transmission frame is fixed on the rotor blade and generates force acting between a support member provided for the force transmission frame and a driven element in an orthogonal direction to a direction of centrifugal force of the rotor blade based on a change in the length of the piezoelectric element device when the piezoelectric element device is excited. In the piezoelectric control apparatus, a first holder allows a relative movement to the rotor blade of the force transmission frame in the orthogonal direction to the direction of centrifugal force within a limited range, and is bendable in the orthogonal direction to the direction of centrifugal force although fixing the force transmission frame on the rotor blade in the direction of centrifugal force. A second holder is bendable in the direction of centrifugal force although relatively fixing the support member provided for the force transmission frame on the rotor blade in the direction orthogonal to the direction of centrifugal force and allows a relative movement of the support member to the rotor blade of the force transmission frame in the direction of centrifugal force within a limited range.
Japanese Laid Open Patent Application (JP-P2002-234499A) discloses a flap structure with a flap driving section into a rotor blade, which can adjust and maintain a flap function through inspection without substantially influencing the rotor blade. The rotor blade includes a flap and a flap driving section. A flap is provided outside the blade and the flap driving section is provided inside the blade. In the lift force generating blade, a blade chamber having an opening portion in a direction of a posterior edge of a wing is formed, and at least one casing is inserted from the opening portion and fixed to the inside of a blade chamber, and the casing incorporates at least one flap driving part and a flap.
Japanese Laid Open Patent Application (JP-P2002-89453A) discloses a hydraulic pressure controlling apparatus suitable for downsizing the apparatus and reducing costs. The hydraulic pressure controlling apparatus includes a pump for performing a pumping action by reciprocating a pump piston provided in a giant-magnetostrictive material through applying a current from a power source to a coil to stretch and shorten the giant-magnetostrictive element arranged in a central portion of the coil by magnetostrictive phenomenon, and a controlled portion which operates depending on discharge pressure from the pump. The hydraulic pressure controlling apparatus includes a current detection section adapted to detect the current passing the coil of the pump; and to estimate the discharge pressure of the pump based on the current detected by the detection section.